1. Technical Field
The present invention relates generally to an apparatus and method for correcting the location of a base station and, more particularly, to an apparatus and method for correcting the location of a base station, which analyze and detect whether a wireless communication infrastructure, such as a base station, the location of which is stored in a location database (DB), has been moved or deleted or whether a new base station has been added, by means of scan data transmitted by users, and which utilize the analyzed and detected information for correcting/updating the location DB.
2. Description of the Related Art
Location estimation technologies using wireless communication infrastructures are present in various schemes depending on the type of infrastructures and the range of services. For example, a Global Navigation Satellite System (GNSS) denotes a system for determining a user's location using satellite signals in orbit around the Earth. Similarly, the U.S. Global Positioning System (GPS), Russian Global Navigation Satellite System (GLONASS), European Galileo, etc. are currently operated or are expected to be operated.
Such a GNSS provides a high location precision of about 10 m or less and high availability in a flatland or a suburban area in which a Direct Line of Sight (DLOS) is directly ensured between satellites and a receiver. However, in a congested metropolitan area corresponding to a Non-Line of Sight (NLOS) area, there is a disadvantage in that a location error reaches 50 m due to multi-path errors, and, especially in indoor areas, it is difficult to determine location because reception sensitivity is deteriorated to make it impossible to acquire signals.
Among other wireless communication infrastructures, cellular-based location estimation technology refers to technology for determining the location of a user using the location information and measurement signals of a mobile communication base station. In detail, cellular-based location estimation technology is classified into Cell-ID, Enhanced-Observed Time Difference (E-OTD), Advanced-Forward Link Trilateration (AFLT) depending on the number of base stations from which a terminal device is capable of receiving signals. Due to the characteristics of mobile communication infrastructures having most urban and suburban areas as a service range, cellular-based location estimation technology is advantageous in that the location may be determined even in indoor areas as well as outdoor areas. However, it is difficult to apply such a cellular-based location estimation technology to indoor/outdoor navigation services requiring a location precision of about several meters because the precision of location estimation varies according to the arrangement density of base stations and a relatively low location precision of an average of about 100 to 800 m is implemented.
Assisted-GNSS denotes technology for acquiring assistant information from a location estimation server so as to improve minimum reception signal sensitivity of a GNSS receiver contained in a user terminal device and shorten the initial location determination time (Time to First Fix). Assisted-GNSS enables fast location determination using a GNSS in a congested metropolitan area corresponding to a weak signal environment, but it is impossible to obtain large effects because signal intensity is very low in indoor areas.
Upon estimating location in indoor/outdoor areas, a problem of discontinuous and interrupted communication occurs, and thus methods usable in both indoor and outdoor areas are developed. A representative of those methods is a Wi-Fi-based location estimation technology. Such a Wi-Fi-based location estimation technology may be chiefly classified into a location database (DB)-based technique and a radio map DB-based technique.
A location DB includes information, such as the identifiers, locations, transmission signal intensities, and signal attenuation coefficients of Wi-Fi Access Points (APs) (i.e., base stations) present in a service area. An agent that calculates locations receives such a location DB and estimates locations using a method, such as Cell-ID, triangulation or Weighted Centroid Localization (WCL).
A radio map DB includes information such as base station information, signal intensities, and various types of statistical information that are received from a plurality of preset reference locations within a service area. An agent that calculates locations compares currently found positioning resources with signal intensities or the like recorded in the radio map DB, and estimates a reference location having the most similar information to be a current location.
Generally, the size of a location DB is relatively small in proportion to the number of base stations installed in a service area. In contrast, a radio map DB is larger than a location DB in proportion to the multiplication of the number of constructed reference locations by the number of base stations. Further, upon estimating locations using a radio map DB, all radio maps related to found information must be compared and correlations therebetween must be analyzed, and thus a longer time is required compared to the location DB-based technique.
Meanwhile, upon estimating locations based on a location DB, location precision is directly influenced by the arrangement and number of base stations, and thus a deviation in performance is large. In contrast, generally, when radio map DBs are densely constructed, relatively precise and stable (having less deviation) performance is exhibited.
When a generally constructed location DB representation method is described in the case of, for example, Wi-Fi, the following Table 1 is given.
TABLE 1DB itemExample of Wi-FiBase station uniqueMAC addressidentifierBase station aliasSSIDBase station locationLatitude, longitude, and altitude, or latitude,longitude, and floor, or indoor relative Xcoordinate, indoor relative Y coordinate, andfloor, etc.Base station transmissionPo (dBm) in Log-distance path-loss modelsignal intensitySignal attenuationα in Log-distance path-loss modelcoefficient......
Since the location DB includes the location, unique identification number, attribute information, etc. of each base station, a terminal may estimate the location using a Cell-ID technique, a triangulation technique, a Weighted Centroid Localization (WCL) technique, or the like by exploiting the included DB information.
For example, when location is estimated using the Cell-ID technique, a location corresponding to a base station having the largest signal intensity, among found base stations (or infrastructures), is determined to be the current location of a terminal.
When location is estimated using the triangulation technique, three or more base stations are selected from among found base stations, signal intensities are converted (estimated) into distances, and the current location of a terminal is calculated using a Least Square method (LSM) or the like.
When location is estimated using the WCL technique, the intensities of signals received from respective base stations are compared with each other using all or some of found base stations, and weights are assigned to the signal intensities, and thus the current location of a terminal is calculated.
If the actual location of a base station has changed due to the influence of various environmental factors, but it is not reflected in the location DB, a large error may occur in the results of the location estimation of the terminal even if any of the above-described location DB-based location estimation methods is used.
Meanwhile, a wireless communication base station, such as a Wi-Fi Access Point (AP), that has short radio coverage and that can be easily installed and removed by a user, may exhibit a frequent change in location with the elapse of time. Accordingly, the location DB in which such information is recorded must be able to desirably reflect such an environmental change. Generally, in order to construct a location DB, radio information, collection locations, etc. must be collected and processed in given areas. However, frequently performing collection/analysis tasks to maintain the location DB in the latest status results in a great waste of time and cost.
As related preceding technology, Korean Patent Application Publication No. 2011-0111851 (entitled “Method of Automatic Registration of Wireless AP”) discloses technology for compensating for the deterioration of precision in location determination due to the information of a moved AP after an AP information map has been constructed, and for continuously improving precision.
As another related preceding technology, there is Korean Patent Application Publication No. 2010-0120924 (entitled “Method and System for Renewal of AP Location Information using Wireless LAN Terminal, and Wireless LAN Terminal therefor”). This patent discloses technology that automatically updates erroneous location information attributable to the location information of a wireless Local Area Network (LAN) AP that is newly installed and the movement of installation locations of previously registered wireless LAN APs, in the DB of a wireless LAN AP location management system via the wireless LAN terminal of a user, thus reducing cost and time required for update after the location information DB of the wireless LAN AP has been initially constructed, with the result that the quality of a wireless LAN-based location information service can be improved.
As further related preceding technology, there is provided Korean Patent Application Publication No. 2005-0063070 (entitled “Apparatus and method of management of wireless AP for enterprise”). This patent discloses technology that, when a communication service provider provides an enterprise wireless LAN service, periodically receives the information of APs installed in a business workplace, immediately updates information required for authentication agency, and periodically checks whether each AP is normally operated so as to process authentication agency of an enterprise wireless LAN and fault management thereof, so that an AP authentication agency service may be favorably processed and AP faults may be immediately repaired, thus supporting the improvement of wireless LAN services for enterprise customers.